Crusades

===Sixth Crusade===
{{main|Sixth Crusade}}
[[File:Friedrich II. mit Sultan al-Kamil.jpg|left|thumb|upright=1.35|alt=Manuscript illumination of five men outside a fortress|[[Frederick II, Holy Roman Emperor|Holy Roman Emperor Frederick{{nbsp}}II]] (left) meets [[al-Kamil]] (right),  illumination from [[Giovanni Villani]]'s ''[[Nuova Cronica]]'' ([[Vatican Library]] ms. Chigiano L VIII 296, 14th{{nbsp}}century).]]

The [[Sixth Crusade]] (1228–1229) was a military expedition to recapture the city of Jerusalem. It began seven years after the failure of the Fifth Crusade and involved very little actual fighting. The diplomatic maneuvering of [[Frederick II, Holy Roman Emperor|Frederick II]]<ref name=":25">Franz Kampers (1909). "[[s:Catholic Encyclopedia (1913)/Frederick II|Frederick II]]". In ''Catholic Encyclopedia''. '''6'''. New York: Robert Appleton Company.</ref> resulted in the Kingdom of Jerusalem regaining some control over Jerusalem for much of the ensuing fifteen years. The Sixth Crusade is also known as the Crusade of Frederick II.<ref name=":232">Van Cleve, Thomas C. (1977). "[http://images.library.wisc.edu/History/EFacs/HistCrus/0001/0002/reference/history.crustwo.i0026.pdf The Crusade of Frederick II]". In Setton, K. ''A History of the Crusades: Volume II''. pp. 377–448.</ref>

Of all the European sovereigns, only Frederick II, the Holy Roman Emperor, was in a position to regain Jerusalem. Frederick was, like many of the 13th-century rulers, a serial ''crucesignatus'',<ref>Markowski, Michael. "[https://www.academia.edu/33305983/Crucesignatus_its_origins_and_early_usage Crucesignatus: its origins and early usage]". ''Journal of Medieval History'' (1984), pp. 157–165.</ref> having taken the cross multiple times since 1215.<ref>Weiler, Björn K. (2006). "Crusade of Emperor Frederick II (1227–1229)". In ''The Crusades: An Encyclopedia''. pp. 313–315.</ref> After much wrangling, an onerous agreement between the emperor and Pope [[Honorius III]] was signed on 25 July 1225 at San Germano. Frederick promised to depart on the Crusade by August 1227 and remain for two years. During this period, he was to maintain and support forces in Syria and deposit escrow funds at Rome in gold. These funds would be returned to the emperor once he arrived at Acre. If he did not arrive, the money would be employed for the needs of the Holy Land.{{sfn|Runciman|1954|pp=171–205|loc=The Emperor Frederick}} Frederick II would go on the Crusade as king of Jerusalem. He married John of Brienne's daughter [[Isabella II of Jerusalem#Marriage with Frederick II|Isabella II]] by proxy in August 1225 and they were formally married on 9 November 1227. Frederick claimed the kingship of Jerusalem despite John having been given assurances that he would remain as king. Frederick took the crown in December 1225. Frederick's first royal decree was to grant new privileges on the Teutonic Knights, placing them on equal footing as the Templars and Hospitallers.{{sfn|Tyerman|2006|pp=739–780|loc=The Crusade of Frederick II, 1227–1229}}

After the Fifth Crusade, the Ayyubid sultan [[al-Kamil]] became involved in civil war in Syria and, having unsuccessfully tried negotiations with the West beginning in 1219, again tried this approach,{{sfn|Gibb|1969|pp=700–702|loc=The Ayyubids from 1221–1229}} offering return of much of the Holy Land in exchange for military support.{{sfn|Maalouf|2006|pp=226–227|loc=Fakhr ad-Din}} Becoming pope in 1227, [[Pope Gregory IX|Gregory IX]] was determined to proceed with the Crusade.<ref>Michael Ott (1909). "[[s:Catholic Encyclopedia (1913)/Pope Gregory IX|Pope Gregory IX]]". In ''Catholic Encyclopedia''. '''6'''. New York: Robert Appleton Company.</ref> The first contingents of Crusaders then sailed in August 1227, joining with forces of the kingdom and fortifying the coastal towns. The emperor was delayed while his ships were refitted. He sailed on 8 September 1227, but before they reached their first stop, Frederick was struck with the plague and disembarked to secure medical attention. Resolved to keep his oath, he sent his fleet on to Acre. He sent his emissaries to inform Gregory IX of the situation, but the pope did not care about Frederick's illness, just that he had not lived up to his agreement. Frederick was excommunicated on 29 September 1227, branded a wanton violator of his sacred oath taken many times.<ref name=":232" />

Frederick made his last effort to be reconciled with Gregory. It had no effect and Frederick sailed from [[Brindisi]] in June 1228. After a stop at Cyprus, Frederick II arrived in Acre on 7 September 1228 and was received warmly by the military orders, despite his excommunication. Frederick's army was not large, mostly German, Sicilian and English.{{sfn|Tyerman|1996|pp=99–101|loc=The Crusade of 1227–1229}} Of the troops he had sent in 1227 had mostly returned home. He could neither afford nor mount a lengthening campaign in the Holy Land given the ongoing [[War of the Keys]] with Rome. The Sixth Crusade would be one of negotiation.{{sfn|Runciman|1954|pp=183–184|loc=Frederick at Acre (1228)}}

After resolving the internecine struggles in Syria, al-Kamil's position was stronger than it was a year before when he made his original offer to Frederick. For unknown reasons, the two sides came to an agreement. The resultant [[Treaty of Jaffa (1229)|Treaty of Jaffa]] was concluded on 18 February 1229, with al-Kamil surrendering Jerusalem, with the exception of some Muslim holy sites, and agreeing to a ten-year truce.{{sfn|Richard|1999|pp=312–318|loc=The Sixth Crusade and the Treaty of Jaffa}} Frederick entered Jerusalem on 17 March 1229 and received the formal surrender of the city by al-Kamil's agent and the next day, crowned himself.{{sfn|Runciman|1954|pp=189–190|loc=Frederick at Jerusalem (1229)}} On 1 May 1229, Frederick departed from Acre and arrived in Sicily a month before the pope knew that he had left the Holy Land. Frederick obtained from the pope relief from his excommunication on 28 August 1230 at the [[Treaty of Ceprano (1230)|Treaty of Ceprano]].{{sfn|Asbridge|2012|pp=562–571|loc=Frederick II's Crusade}}

The results of the Sixth Crusade were not universally acclaimed. Two letters from the Christian side tell differing stories,{{sfn|Munro|1902|pp=24–30|loc=Letters of the Sixth Crusade}} with Frederick touting the great success of the endeavor and the Latin patriarch painting a darker picture of the emperor and his accomplishments. On the Muslim side, al-Kamil himself was pleased with the accord, but others regarded the treaty as a disastrous event.{{sfn|Christie|2014|loc=Document 17: Two sources on the Handover of Jerusalem to Frederick II}} In the end, the Sixth Crusade successfully returned Jerusalem to Christian rule and had set a precedent, in having achieved success on crusade without papal involvement.